1. Field of the Invention
The present invention relates to a vehicle headlight system, and in particular to an automobile headlight system that controls a pulsed power source to energize a set of lighting elements.
2. Related Art
Motor vehicle headlight systems generally allow a set of headlamps to be illuminated in a low beam mode or a high beam mode. Usually, each headlamp includes a low beam filament and a high beam filament, wherein the low beam filaments are energized in the low beam mode and the high beam filaments are energized in the high beam mode. Such a system usually includes two relays and four fuses. One relay is used to energize both low beam filaments at full intensity and the other relay is used to energize both high beam filaments at full intensity. Each fuse is associated with, and provides overload protection, for a particular filament.
The system described above has a number of disadvantages. First, such a system does not allow pulsed power to be applied across the headlamp filaments because pulsed voltage cannot be continuously applied across a relay. Instead, the filaments are continuously energized at a particular voltage level; usually battery voltage minus small voltage drops from the system. Continuously energizing the filaments at high intensity causes high power consumption and shortens the life of the filaments. Also, fuses are mechanical devices that must be manually replaced in the event of a short to ground. When a fuse blows, the vehicle is usually taken to a dealer to replace the fuse for a cost or under warranty. As mechanical devices, fuses can be less reliable than semiconductor devices. Additionally, fuses do not allow the system to sense whether there is an open or short circuit condition in the headlight system and to automatically switch power to an operable filament when a fault condition is present with a particular filament.
Therefore, it is desirable to provide a vehicle headlight system that allows pulsed power to be applied across selected headlight filaments. It is also desirable to provide a vehicle headlight system which includes solid state switching devices to connect the filaments to the power source, and a control element to detect the presence of a fault condition and automatically adjust the headlight system to overcome detected fault conditions.